Wireless terminals are increasingly used to transmit services that create real-time experience for the end user, or user of the terminal. As these services are being transmitted though wireless packet-switched network, operators or service providers must pay attention to the quality of service.
The end user can often experience situations with mobile real-time services where the service is badly corrupted. These incidents are usually caused by mobile network resulting from system malfunction, too high Bit Error Rate, overloading, handovers or inter-system handovers. Problems can be also caused by a malfunctioning mobile terminal. As a result the real-time service may be discontinuous or the video/audio stream quality may be below the acceptable limit. Especially with real time services all the data packets may be delivered to the terminal intact, but the fact that the packets were greatly delayed and jittered is the key factor that indicates the service corruption.
The Real-Time Transport Protocol (RTP) is an Internet protocol standard that specifies a way for programs to manage the real-time transmission of multimedia data over either unicast or multicast network services. RTP is specified in Internet Engineering Task Force (IETF) Request for Comments (RFC) 1889. RTP is commonly used for example in Internet telephony applications. Similar services are emerging on the wireless network systems, such as IMS (IP Multimedia subsystem). RTP does not in itself guarantee real-time delivery of multimedia data since this is dependent on network characteristics.
WO03034685 describes a solution where the volume of transmitted data is determined and sent from terminal to a billing system. The billing system takes into account the sent and received data and obtains the cost of data received by the mobile station.
The problem of this approach is that the network is not aware of the actual quality of the real-time service, how the user has perceived the service. The amount of received data does not necessarily correlate to the quality of real-time services, as they typically require an even data flow.
A 3GPP standard publication TS 22.115, version 6.4.0 describes a solution in which the terminal requests QoS (Quality of Service) parameters that the network either accepts, rejects or alters. These QoS parameters guide the radio and core networks in such a manner that transmission would be realized under these parameters. However, these parameters do not guarantee the QoS level required by the real-time application run by the terminal. The application may still run poorly e.g. due to cell handover, since the QoS parameters are still the same as in the previous cell. The terminal sends information about the received QoS parameters to the core network or to the billing system, where charging may be applied to different QoS schemes. Sending only received QoS parameters back to the network or billing system does not describe the quality of the real-time service.